In cooling water systems, accumulations of clays are troublesome in that they reduce heat transfer efficiency of heat exchangers and the like. Also, accumulations of deposits on cooling tower fill reduce the evaporative efficiency of the cooling tower. In many instances, these deposits must be mechanically cleaned when they are present in excessive amounts. Hydrofluoric acid and ammonium bifluoride are known to dissolve silicas, silicates and clays. These compounds, however, would be unacceptable to remove deposits from surfaces in contact with cooling water systems, for several reasons.
Both compounds are extremely hazardous and toxic. The compounds are also highly corrosive to metals. The ammonia from the ammonium bifluoride is also known to be corrosive to metals made from copper. (Heat exchangers in cooling systems are often made from metals that contain copper.) These compounds also introduce the possibility of calcium fluoride scale formation which would reduce heat transfer. Cement is commonly used to construct cooling tower sumps and other structural parts. Since cement is a silicate, it would dissolve in the presence of the fluoride compounds.
The present invention is directed toward methods and compositions for chemically cleaning clay deposits from metal surfaces, particularly from heat exchange surfaces in cooling water systems, and non-metal surfaces such as plastic cooling tower fill.